Please send me some good links on System Function Calls

Question

Hi,
I want to know more about System Function calls. Please send me some good links on the same.
Eg : CALL 'C_DIR_READ_NEXT'
      ID 'TYPE'   FIELD file-type
      ID 'NAME'   FIELD file-name
      ID 'LEN'    FIELD file-len
      ID 'OWNER'  FIELD file-owner
      ID 'MTIME'  FIELD file-mtime
      ID 'MODE'   FIELD file-mode
      ID 'ERRNO'  FIELD file-errno
      ID 'ERRMSG' FIELD file-errmsg.
Rgds,
Raghavendra.

Answer 1

Hi,
<u><b>CALL - Call a System Function:</b></u>
<b>Note</b>
This statement is for internal use only.
It cannot be used in application programs.
As of Release 6.20, you should use Kernel Methods instead of system functions.
<b>Syntax</b>
CALL cfunc.
Addition:
... ID id1 FIELD f1 ... ID idn FIELD fn
<b>Effect</b>
Calls the system function cfunc. The relevant function must exist in the file sapactab.h. If you change or recreate a function, you have to compile and link the SAP kernel again. For this, you need the C source code files.
Normally, external programs should be called by RFC with CALL FUNCTION ... DESTINATION.
<b>Addition</b>
... ID id1 FIELD f1 ... ID idn FIELD fn
<b>Effect</b>
Passes fields to the called program by reference. With "ID id1", you specify the name of a formal parameter, and with "FIELD f1" the relevant field from the ABAP/4 program. If a formal parameter expects an internal table, the latter is passed in the form "FIELD tab[]".
Example
DATA RESULT(8).
CALL 'MULTIPLY' ID 'P1'  FIELD '9999'
                ID 'P2'  FIELD '9999'
                ID 'RES' FIELD RESULT.
<b>Note</b>
With some critical C functions, the system automatically performs an authorization check. If the user does not have the appropriate authorization, a runtime error occurs. You can check the authorization with the function module AUTHORITY_CHECK_C_FUNCTION.
<b>Exceptions</b>
Non-Catchable Exceptions
Cause: You do not have the authorization to call this C function.
Runtime Error: CALL_C_FUNCTION_NO_AUTHORITY
Cause: The system function specified is unknown.
Runtime Error: CALL_C_FUNCTION_NOT_FOUND
Cause: The system function SYSTEM is deactivated (in CALL 'SYSTEM')
Runtime Error: CALL_SYSTEM_DISABLED
Regards,
Bhaskar